Validation of Cadherin HAV6 Peptide in the Transient Modulation of the Blood-Brain Barrier for the Treatment of Brain Tumors

Therapeutic approaches for targeting the pediatric brain tumor microenvironment

Central nervous system (CNS) tumors are the most frequent solid malignant tumors in pediatric patients and are the leading cause of tumor-related death in children. Treatment for this heterogeneous group of tumors consists of various combinations of safe maximal surgical resection, chemotherapy, and radiation therapy which offer a cure for some children but often cause debilitating adverse late effects in others. While therapies targeting the tumor microenvironment (TME) like immune checkpoint inhibition (ICI) have been successful in treating some cancers, these therapies failed to exhibit treatment efficacy in the majority of pediatric brain tumors in the clinic. Importantly, the pediatric TME is unique and distinct from adult brain tumors and designing therapies to effectively target these tumors requires understanding the unique biology of pediatric brain tumors and the use of translational models that recapitulate the TME. Here we describe the TME of medulloblastoma (MB) and diffuse midline glioma (DMG), specifically diffuse intrinsic pontine glioma (DIPG), and further present the current drug delivery approaches and clinical administration routes targeting the TME in these tumors, including preclinical and clinical studies.

Delivery of Neuroregenerative Proteins to the Brain for Treatments of Neurodegenerative Brain Diseases

Neurodegenerative brain diseases such as Alzheimer's disease (AD), multiple sclerosis (MS), and Parkinson's disease (PD) are difficult to treat. Unfortunately, many therapeutic agents for neurodegenerative disease only halt the progression of these diseases and do not reverse neuronal damage. There is a demand for finding solutions to reverse neuronal damage in the central nervous system (CNS) of patients with neurodegenerative brain diseases. Therefore, the purpose of this review is to discuss the potential for therapeutic agents like specific neurotrophic and growth factors in promoting CNS neuroregeneration in brain diseases. We discuss how BDNF, NGF, IGF-1, and LIF could potentially be used for the treatment of brain diseases. The molecule's different mechanisms of action in stimulating neuroregeneration and methods to analyze their efficacy are described. Methods that can be utilized to deliver these proteins to the brain are also discussed.

Mechanism of the blood-brain barrier modulation by cadherin peptides

Aim

This study was aimed at finding the binding site on the human E-cadherin for Ala-Asp-Thr Cyclic 5 (ADTC5), ADTC7, and ADTC9 peptides as blood-brain barrier modulator (BBBM) for determining their mechanism of action in modulating the blood-brain barrier (BBB).

Methods

ADTC7 and ADTC9 were derivatives of ADTC5 where the Val6 residue in ADTC5 was replaced by Glu6 and Tyr6 residues, respectively. The binding properties of ADTC5, ADTC7, and ADTC9 to the extracellular-1 (EC1) domain of E-cadherin were evaluated using chemical shift perturbation (CSP) method in the two dimensional (2D) 1H-15N-heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectroscopy. Molecular docking experiments were used to determine the binding sites of these peptides to the EC1 domain of E-cadherin.

Results

This study indicates that ADTC5 has the highest binding affinity to the EC1 domain of E-cadherin compared to ADTC7 and ADTC9, suggesting the importance of the Val6 residue as shown in our previous in vitro study. All three peptides have a similar binding site at the hydrophobic binding pocket where the domain swapping occurs. ADTC5 has a higher overlapping binding site with ADTC7 than that of ADTC9. Binding of ADTC5 on the EC1 domain influences the conformation of the EC1 C-terminal tail.

Conclusions

These peptides bind the domain swapping region of the EC1 domain to inhibit the trans-cadherin interaction that creates intercellular junction modulation to increase the BBB paracellular porosity.

Selective Uptake of Macromolecules to the Brain in Microfluidics and Animal Models Using the HAVN1 Peptide as a Blood-Brain Barrier Modulator

Monoclonal antibodies (mAbs) possess favorable pharmacokinetic properties, high binding specificity and affinity, and minimal off-target effects, making them promising therapeutic agents for central nervous system (CNS) disorders. However, their development as effective therapeutic and diagnostic agents for brain disorders is hindered by their limited ability to efficiently penetrate the blood-brain barrier (BBB). Therefore, it is crucial to develop efficient delivery methods that enhance the penetration of antibodies into the brain. Previous studies have demonstrated the potential of cadherin-derived peptides (i.e., ADTC5, HAVN1 peptides) as BBB modulators (BBBMs) to increase paracellular porosities for penetration of molecules across the BBB. Here, we test the effectiveness of the leading BBBM peptide, HAVN1 (Cyclo(1,6)SHAVSS), in enhancing the permeation of various monoclonal antibodies through the BBB using both in vitro and in vivo systems. In vitro, HAVN1 has been shown to increase the permeability of fluorescently labeled macromolecules, such as a 70 kDa dextran, 50 kDa Fab1, and 150 kDa mAb1, by 4- to 9-fold in a three-dimensional blood-brain barrier (3D-BBB) microfluidics model using a human BBB endothelial cell line (i.e., hCMEC/D3). HAVN1 was selective in modulating the BBB endothelial cell, compared to the pulmonary vascular endothelial (PVE) cell barrier. Co-administration of HAVN1 significantly improved brain depositions of mAb1, mAb2, and Fab1 in C57BL/6 mice after 15 min in the systemic circulation. Furthermore, HAVN1 still significantly enhanced brain deposition of mAb2 when it was administered 24 h after the administration of the mAb. Lastly, we observed that multiple doses of HAVN1 may have a cumulative effect on the brain deposition of mAb2 within a 24-h period. These findings offer promising insights into optimizing HAVN1 and mAb dosing regimens to control or modulate mAb brain deposition for achieving desired mAb dose in the brain to provide its therapeutic effects.

Enhancing Antibody Exposure in the Central Nervous System: Mechanisms of Uptake, Clearance, and Strategies for Improved Brain Delivery

Antibodies (mAbs) are attractive molecules for their application as a diagnostic and therapeutic agent for diseases of the central nervous system (CNS). mAbs can be generated to have high affinity and specificity to target molecules in the CNS. Unfortunately, only a very small number of mAbs have been specifically developed and approved for neurological indications. This is primarily attributed to their low exposure within the CNS, hindering their ability to reach and effectively engage their potential targets in the brain. This review discusses aspects of various barriers such as the blood-brain barrier (BBB) and blood-cerebrospinal fluid (CSF) barrier (BCSFB) that regulate the entry and clearance of mAbs into and from the brain. The roles of the glymphatic system on brain exposure and clearance are being described. We also discuss the proposed mechanisms of the uptake of mAbs into the brain and for clearance. Finally, several methods of enhancing the exposure of mAbs in the CNS were discussed, including receptor-mediated transcytosis, osmotic BBB opening, focused ultrasound (FUS), BBB-modulating peptides, and enhancement of mAb brain retention.

Peptide-Based Agents for Cancer Treatment: Current Applications and Future Directions

Peptide-based strategies have received an enormous amount of attention because of their specificity and applicability. Their specificity and tumor-targeting ability are applied to diagnosis and treatment for cancer patients. In this review, we will summarize recent advancements and future perspectives on peptide-based strategies for cancer treatment. The literature search was conducted to identify relevant articles for peptide-based strategies for cancer treatment. It was performed using PubMed for articles in English until June 2023. Information on clinical trials was also obtained from ClinicalTrial.gov. Given that peptide-based strategies have several advantages such as targeted delivery to the diseased area, personalized designs, relatively small sizes, and simple production process, bioactive peptides having anti-cancer activities (anti-cancer peptides or ACPs) have been tested in pre-clinical settings and clinical trials. The capability of peptides for tumor targeting is essentially useful for peptide-drug conjugates (PDCs), diagnosis, and image-guided surgery. Immunomodulation with peptide vaccines has been extensively tested in clinical trials. Despite such advantages, FDA-approved peptide agents for solid cancer are still limited. This review will provide a detailed overview of current approaches, design strategies, routes of administration, and new technological advancements. We will highlight the success and limitations of peptide-based therapies for cancer treatment.

The Tumor Microenvironment of Medulloblastoma: An Intricate Multicellular Network with Therapeutic Potential

Medulloblastoma (MB) is a heterogeneous disease in which survival is highly affected by the underlying subgroup-specific characteristics. Although the current treatment modalities have increased the overall survival rates of MB up to 70-80%, MB remains a major cause of cancer-related mortality among children. This indicates that novel therapeutic approaches against MB are needed. New promising treatment options comprise the targeting of cells and components of the tumor microenvironment (TME). The TME of MB consists of an intricate multicellular network of tumor cells, progenitor cells, astrocytes, neurons, supporting stromal cells, microglia, immune cells, extracellular matrix components, and vasculature systems. In this review, we will discuss all the different components of the MB TME and their role in MB initiation, progression, metastasis, and relapse. Additionally, we briefly introduce the effect that age plays on the TME of brain malignancies and discuss the MB subgroup-specific differences in TME components and how all of these variations could affect the progression of MB. Finally, we highlight the TME-directed treatments, in which we will focus on therapies that are being evaluated in clinical trials.

A Historical Review of Brain Drug Delivery

The history of brain drug delivery is reviewed beginning with the first demonstration, in 1914, that a drug for syphilis, salvarsan, did not enter the brain, due to the presence of a blood-brain barrier (BBB). Owing to restricted transport across the BBB, FDA-approved drugs for the CNS have been generally limited to lipid-soluble small molecules. Drugs that do not cross the BBB can be re-engineered for transport on endogenous BBB carrier-mediated transport and receptor-mediated transport systems, which were identified during the 1970s-1980s. By the 1990s, a multitude of brain drug delivery technologies emerged, including trans-cranial delivery, CSF delivery, BBB disruption, lipid carriers, prodrugs, stem cells, exosomes, nanoparticles, gene therapy, and biologics. The advantages and limitations of each of these brain drug delivery technologies are critically reviewed.

Target specific tight junction modulators

Intercellular tight junctions represent a formidable barrier against paracellular drug absorption at epithelia (e.g., nasal, intestinal) and the endothelium (e.g., blood-brain barrier). In order to enhance paracellular transport of drugs and increase their bioavailability and organ deposition, active excipients modulating tight junctions have been applied. First-generation of permeation enhancers (PEs) acted by unspecific interactions, while recently developed PEs address specific physiological mechanisms. Such target specific tight junction modulators (TJMs) have the advantage of a defined specific mechanism of action. To date, merely a few of these novel active excipients has entered into clinical trials, as their lack in safety and efficiency in vivo often impedes their commercialisation. A stronger focus on the development of such active excipients would result in an economic and therapeutic improvement of current and future drugs.

Adoptive Cell Therapy: A Novel and Potential Immunotherapy for Glioblastoma

Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults with very poor prognosis and few advances in its treatment. Recently, fast-growing cancer immunotherapy provides a glimmer of hope for GBM treatment. Adoptive cell therapy (ACT) aims at infusing immune cells with direct anti-tumor activity, including tumor-infiltrating lymphocyte (TIL) transfer and genetically engineered T cells transfer. For example, complete regressions in patients with melanoma and refractory lymphoma have been shown by using naturally tumor-reactive T cells and genetically engineered T cells expressing the chimeric anti-CD19 receptor, respectively. Recently, the administration of ACT showed therapeutic potentials for GBM treatment as well. In this review, we summarize the success of ACT in the treatment of cancer and provide approaches to overcome some challenges of ACT to allow its adoption for GBM treatment.

Non-invasive Brain Delivery and Efficacy of BDNF in APP/PS1 Transgenic Mice as a Model of Alzheimer's Disease

Neurotrophic factors such as brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) have been demonstrated for their potential as a neuroregenerative treatment of Alzheimer's disease (AD). Unfortunately, most proteins cannot be effectively delivered into the brain from the blood stream due to the presence of the blood-brain barrier (BBB). In this study, we delivered BDNF using ADTC5 as BBB modulator (BBBM) into the brains of transgenic APP/PS1 mice, a mouse model for AD. As controls, two groups of APP/PS1 mice were treated with BDNF alone and vehicle, respectively. All three groups were subjected to behavioral/cognitive assessments in Y-maze and novel object recognition (NOR) tests as well as evaluation of the brain markers activated by BDNF. The results showed that BDNF + ADTC5 group performed significantly better in both the Y-maze and NOR assessments compared to mice that received BDNF alone or vehicle. In addition, significant upregulations of NG2 receptors as well as EGR1 and ARC mRNA transcripts were observed in the brain cortex of mice treated with BDNF + ADTC5, further indicating the efficacy of delivered BDNF in the brain. There were high plaque loads in all groups of mice, suggesting no influence of BDNF on the plaque formation. In summary, ADTC5 can deliver BDNF into the brains of APP/PS1 mice and the activity of BDNF in improving cognitive function was likely due to improvement in synaptic plasticity via NG2 glia cells and not by reducing the plaque load.

Noninvasive Brain Delivery and Efficacy of BDNF to Stimulate Neuroregeneration and Suppression of Disease Relapse in EAE Mice

The number of FDA-approved protein drugs (biologics), such as antibodies, antibody-drug conjugates, hormones, and enzymes, continues to grow at a rapid rate; most of these drugs are used to treat diseases of the peripheral body. Unfortunately, most of these biologics cannot be used to treat brain diseases such as Alzheimer's disease (AD), multiple sclerosis (MS), and brain tumors in a noninvasive manner due to their inability to permeate the blood-brain barrier (BBB). Therefore, there is a need to develop an effective method to deliver protein drugs into the brain. Here, we report a proof of concept to deliver a recombinant brain-derived neurotrophic factor (BDNF) to the brains of healthy and experimental autoimmune encephalomyelitis (EAE) mice via intravenous (iv) injections by co-administering BDNF with a BBB modulator (BBBM) peptide ADTC5. Western blot evaluations indicated that ADTC5 enhanced the brain delivery of BDNF in healthy SJL/elite mice compared to BDNF alone and triggered the phosphorylation of TrkB receptors in the brain. The EAE mice treated with BDNF + ADTC5 suppressed EAE relapse compared to those treated with BDNF alone, ADTC5 alone, or vehicle. We further demonstrated that brain delivery of BDNF induced neuroregeneration via visible activation of oligodendrocytes, remyelination, and ARC and EGR1 mRNA transcript upregulation. In summary, we have demonstrated that ADTC5 peptide modulates the BBB to permit noninvasive delivery of BDNF to exert its neuroregeneration activity in the brains of EAE mice.

In Vivo Brain Delivery and Brain Deposition of Proteins with Various Sizes

It is very challenging to develop protein drugs for the treatment of brain diseases; this is due to the difficulty in delivering them into the brain because of the blood-brain barrier (BBB). Thus, alternative delivery methods need further exploration for brain delivery of proteins to diagnose and treat brain diseases. Previously, ADTC5 and HAV6 peptides have been shown to enhance the in vivo brain delivery of small- and medium-size molecules across the BBB. This study was carried out to evaluate the ability of ADTC5 and HAV6 peptides to enhance delivery of proteins of various sizes, such as 15 kDa lysozyme, 65 kDa albumin, 150 kDa IgG mAb, and 220 kDa fibronectin, into the brains of C57BL/6 mice. Each protein was labeled with IRdye800CW, and a quantitative method using near IR fluorescence (NIRF) imaging was developed to determine the amount of protein delivered into the brain. ADTC5 peptide significantly enhanced brain delivery of lysozyme, albumin, and IgG mAb but not fibronectin compared to controls. In contrast, HAV6 peptide significantly enhanced the brain delivery of lysozyme but not albumin and IgG mAb. Thus, there is a cutoff size of proteins that can be delivered by each peptide. The distribution of delivered protein in other organs such as liver, spleen, lung, kidney, and heart could be influenced by HAV6 and ADTC5. In summary, ADTC5 is a better BBB modulator than HAV6 in delivering various sizes of proteins into the brain, and the size of the protein affects its brain delivery.

Improving In Vivo Brain Delivery of Monoclonal Antibody Using Novel Cyclic Peptides

Many proteins can be used to treat brain diseases; however, the presence of the blood–brain barrier (BBB) creates an obstacle to delivering them into the brain. Previously, various molecules were delivered through the paracellular pathway of the BBB via its modulation, using ADTC5 and HAV6 peptides. This study goal was to design new cyclic peptides with N-to-C terminal cyclization for better plasma stability and modulation of the BBB. Cyclic HAVN1 and HAVN2 peptides were derived from a linear HAV6 peptide. Linear and N-to-C terminal cyclic ADTHAV peptides were designed by combining the sequences of ADTC5 and HAV6. These novel cyclic peptides were used to deliver an IRdye800CW-labeled IgG monoclonal antibody into the brain. Cyclic HAVN1 and HAVN2 peptides deliver IgG into the brain, while the parent linear HAV6 peptide does not. Cyclic and linear ADTHAV and ADTC5 peptides enhanced brain delivery of IgG mAb, in which cyclic ADTHAV peptide was better than linear ADTHAV (p = 0.07). Cyclic ADTHAV and ADTC5 influenced the distribution of IgG mAb in other organs while HAV6, HAVN1 and HAVN2 did not. In summary, the novel cyclic peptides are generally better BBB modulators than their linear counterparts for delivering IgG mAb into the brain.

Drug Delivery Technology Development in Canada

Canada has a long and rich history of ground-breaking research in drug delivery within academic institutions, pharmaceutical industry and the biotechnology community. Drug delivery refers to approaches, formulations, technologies, and systems for transporting a pharmaceutical compound in the body as needed to safely achieve its desired therapeutic effect. It may involve rational site-targeting, or facilitating systemic pharmacokinetics; in any case, it is typically concerned with both quantity and duration of the presence of the drug in the body. Drug delivery is often approached through a drug’s chemical formulation, medical devices or drug-device combination products. Drug delivery is a concept heavily integrated with dosage form development and selection of route of administration; the latter sometimes even being considered part of the definition. Drug delivery technologies modify drug release profile, absorption, distribution and elimination for the benefit of improving product efficacy and safety, as well as patient convenience and adherence. Over the past 30 years, numerous Canadian-based biotechnology companies have been formed stemming from the inventions conceived and developed within academic institutions. Many have led to the development of important drug delivery products that have enhanced the landscape of drug therapy in the treatment of cancer to infectious diseases. This Special Issue serves to highlight the progress of drug delivery within Canada. We invited articles on all aspects of drug delivery sciences from pre-clinical formulation development to human clinical trials that bring to light the world-class research currently undertaken in Canada for this Special Issue.